1. Field of the Invention
This invention relates to a seat belt take-up device for a vehicle, and more particularly to a seat belt take-up device provided with an emergency-locking mechanism for locking draw-out of webbing and safely restraining a seat occupant when there is a speed change of the vehicle above a predetermined value.
2. Description of the Prior Art
There have heretofore been proposed numerous seat belt take-up devices provided with emergency-locking mechanisms of such type, but these devices tend to have a complicated mechanism to accomplish emergency-lock with high accuracy and reliability and numerous expensive parts.
Seat belt take-up devices provided with conventional emergency-locking mechanisms, have been generally one of two types, namely, the type in which the draw-out acceleration of webbing is used as an agency to cause the emergency-locking mechanism to act and the type in which a speed change of a vehicle is directly sensed by an inertia displacement member such as a pendulum or the like to thereby cause the emergency-locking mechanism to act. Devices comprising these two types of devices combined together to provide more reliable emergency-locking of the seat belt take-up device have also been used, but such devices involve the necessity of incorporating two complicated emergency-locking mechanisms into a single take-up device and this leads to bulkiness of the entire device and expensiveness of the device resulting from a greater number of parts.